Analog video may be received through broadcast, cable, and VCRs. The reception is often corrupted by noise, and therefore to improve the visual quality, noise reduction may be needed. Digital video may be received through broadcast, cable, satellite, Internet, and video discs. Digital video may be corrupted by noise, which may include coding artifacts, and to improve the visual quality and coding gain, noise reduction may be beneficial. Various noise filters have been utilized in video communication systems such as set top boxes. However, inaccurate noise characterization, especially during scenes with motion, may result in artifacts caused by the filtering, which are more visually detrimental than the original noise.
In video system applications, random noise present in video signals, such as National Television System(s) Committee (NTSC) or Phase Alternating Line (PAL) analog signals, for example, may result in images that are less than visually pleasing to the viewer and the temporal noise may reduce the video encoder coding efficiency. As a result, the temporal noise may affect the video quality of the encoded video stream with a given target bitrate. To address this problem, spatial and temporal noise reduction (NR) operations may be utilized to remove or mitigate the noise present. Traditional NR operations may use either infinite impulse response (IIR) filtering based methods or finite impulse response (FIR) filtering based methods. Temporal filtering may be utilized to significantly attenuate temporal noise. However, temporal filtering may result in visual artifacts such as motion trails, jittering, and/or wobbling at places where there is object motion when the amount of filtering is not sufficiently conservative. Spatial filtering may attenuate significantly high frequency noise or some narrow pass disturbing signals. However, spatial filtering may also attenuate the content spectrum, which may introduce blurriness artifacts in the active spatial filter areas.
Color information carried by a composite television (TV) signal may be modulated in quadrature upon a subcarrier. The subcarrier may have a frequency corresponding to the line scan frequency in a manner that may interleave the color information about the subcarrier between energy spectra of the luminance baseband signal. In color television systems such as NTSC and PAL, the color information comprises luminance (Y) and chrominance (C) information sharing a portion of the total signal bandwidth. Thus, a Y/C separation procedure in the receiving end may be required to extract the luminance and chrominance information individually. The luminance and chrominance information of some image areas, especially in image areas such as a motion edge of high frequency luminance, may not be distinguishable due to imperfect encoding techniques. For example, a television demodulator may incorrectly demodulate high frequency luminance information as chrominance information, causing color artifacts on vertical edges. These color artifacts may include, for example, color ringing, color smearing, and the display of color rainbows in place of high-frequency gray-scale information.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.